Considerable time and effort are expended by research chemists in the search for new and inexpensive chemicals which can be used as flavor and fragrance modifiers or enhancers in various consumable materials. These substances are used to reduce or replace those natural compounds presently employed which are in diminishing or sporadic supply. They also are employed in creating entirely new flavors and fragrances.
Certain chemicals having the pyran ring have been found to be useful for imparting fragrance and/or flavor to compositions of which they are constituents. For example, Japanese application Ser. No. 7,4011-073 published Mar. 14, 1974, discloses 2,5-diethyltetrahydropyran chemicals having a rose-like scent, while 3-hydroxy-2-methyl-1,4-pyran, or maltol, is disclosed in "Perfume and Flavor Chemicals", Arctander Vol. II, No. 1831, as possessing "a warm-fruity, caramellic-sweet odor with emphasis on the caraway note in the dry state."
U.S. Pat. No. 3,901,924, granted Aug. 26, 1975, discloses certain 1,1-dialkylnaphthopyrans, as well as certain chypre and fougere type perfume formulations of which these pyrans are constituents. Examples of these pyrans are the following: ##STR2## wherein each of R.sup.1 and R.sup.2 represents a lower alkyl group.
U.S. Pat. No. 4,010,286, granted Mar. 1, 1977, discloses various substituted spiropyrans which exhibit a variety of odors and/or flavors, including those characterized as spicy, dill, green, floral, herbal, eucalyptol-like, woody, fruity, berry-like, sweet, minty and weedy, and which are useful as flavoring and fragrance imparters or modifiers. Examples of the spiropyrans disclosed in this patent are the following: ##STR3## wherein the dashed lines represent carbon-carbon double bonds; and wherein the presence of two dashed lines in a single structure representation indicates a mixture of double bond isomers. Still other spiropyrans which are disclosed are the product of the reaction of dihydro verdyl ketone or verdyl ketone with 3-methyl-3-buten-1-01, which is represented by the following formula: ##STR4##
Methods of preparation of other pyran chemicals have also been disclosed in the prior art. For example, U.S. Pat. No. 2,422,648, granted June 17, 1947, discloses a method for the preparation of certain dihydropyran chemicals which comprises reacting a ketone with an unsaturated alcohol containing an unsaturated tertiary carbon atom linked directly by a single bond to a saturated carbon atom which is directly attached to the carbinol carbon atom, in the presence of an acidic condensation catalyst at a temperature of about about 50.degree. C., but not substantially above the temperature of dehydration of the alcohol.
In addition, methods of preparation of both rose oxide and nerol oxide, known odoriferous components of Bulgarian rose oil, are disclosed in Tetrahedron Letters, 51, 4507 (1970) by J. H. P. Tyman and B. J. Willis. These chemicals are prepared from the reaction of 3-methyl-2-butenal with 2-methyl-1-buten-4-ol under acidic conditions.
The chemicals described in each of the above patents and articles are different in kind from the chemicals of the instant invention from a structural standpoint, and from the standpoint of their fragrance properties. The chemicals of the instant invention possess unexpected, unobvious and advantageous properties from the standpoint of quality, character of fragrance when used in fragrance compositions.
The chemicals of this invention also are related to the "norcamphanyl"-substituted pyrans of our co-pending application Ser. No. 950,598 filed Oct. 12, 1978 now U.S. Pat. No. 4,197,246 granted Apr. 8, 1980, and which may be represented by the structural formula. ##STR5##
Structurally, the chemicals of this invention differ from those of our prior application in that there is no more than one substituent at the 3-position of the norbornyl nucleus, and there may be a double bond between the 5- and 6-carbons. Furthermore, the chemicals differ materially in their odor characteristics. The chemicals of this invention are characterized by green, woody, sweet, fruity, aldehydic odors, whereas the chemicals of our prior application are characterized by soft, dry woody odors with green pepper notes.